Conventional variable valve mechanisms are known, that can make valve opening timing and closing timing (hereinafter collectively referred to as valve timing) and a lift amount of an intake valve and an exhaust valve, variable. The variable valve mechanisms greatly contribute to the improvement of thermal efficiency of internal combustion engines by realizing the valve timing and the lift amount suitable for an operating state of internal combustion engines. On the other hand, an in-cylinder direct injection internal combustion engine is an internal combustion engine that injects fuel applied with pressure (pressurized) by a high pressure fuel pump directly into a cylinder from a fuel injection valve. In recent years, regulations on the exhaust performance of internal combustion engines have been strengthened on a worldwide scale, and in particular in in-cylinder direct injection internal combustion engines, various techniques aimed at improving homogeneity and reducing unburned fuel as countermeasures have been invented and practically used.
Examples of such countermeasure techniques include, for example, a method of increasing the fuel pressure of injection into the cylinder to promote atomization of the fuel in order to improve homogeneity, and multistage injection control of suppressing the fuel injection length (time width of fuel injection), to reduce fuel adhesion to the piston and wall flow in the cylinder. However, when these technologies are applied, it is indispensable to mechanically improve the fuel system and control the fuel system with high accuracy. For example, in order to achieve a high fuel pressure, an improvement of a high pressure fuel pump suitable for the high fuel pressure is desired, so that a return spring corresponding to the fluid force of the high fuel pressure fuel is required, while responsiveness in operation deteriorates, and therefore, it is necessary to improve additional mechanisms and components that can satisfy these requirements. However, in such a complicated configuration, there is a possibility that noise accompanying driving of the high pressure fuel pump becomes high or the number of times of noise increases. As the application range of multistage injection control is required to increase and the number of times of multistage injection is required to increase, the number of times of noise accompanying driving of the fuel injection valve tends to increase as a whole.
Under such circumstances, it is concerned that, as compared with the prior art, drive noises generated when each of the high pressure fuel pump and the fuel injection valve is driven overlap each other, thereby increasing the opportunity (number of times) of synthetic noise that causes sensuously uncomfortable feeling. In particular, the noise during the idling operation is not acceptable from the viewpoint of merchantability.
As a technique for reducing such synthetic noise, there is a technique that has already been devised, the technique of making driving of a high pressure fuel pump and a fuel injection valve, specifically, opening and closing timing of a spill valve for adjusting the pressurization state of a high pressure fuel pump, the drive timing (injection timing) of a fuel injection valve, or the like, variable, on the basis of peak noise of synthetic noise (for example, see PTL 1 and PTL 2 below).